Quality assurance and the evaluation of uncertainties in environmental measurements

Radioactivity environmental monitoring programmes have been established to provide relevant information on radioactivity levels in all compartments of the biosphere: compliance against regulatory limits involves that large numbers of results from environmental radioactive determinations be compared to basic standards, to make important decisions on the potential risk to humans or the environment itself. The reliability of the assessment obtained from these programmes implies that laboratories producing the analytical data be able to provide results of the required quality. The confidence to be placed in results is possible only if a quantitative and reliable expression of their relative quality, the associated uncertainty, is assessed, obviously it has implications for decision purposes. The environmental measurements are frequently performed at levels where the radionuclide of interest cannot be distinguished from natural background levels and the relative uncertainty associated with the result tends to increase. This is a "conflicting domain" where some confusion exists due not only to the difficulty of establishing decision/detection levels, but also due to the numerous existing criteria, terminology and formulation. The necessary comparability of the results from laboratories at international level involves, further to the implementation of a quality, assurance program, the harmonisation of criteria, sampling procedures, calculations, or the reporting of results agreed upon fundamental principles and international standards. This paper reviews and describes concepts relevant to uncertainty, measurement and criteria at the "conflicting domain", based on recent international standards. Some recommendations are outlined, aiming to contribute to the achievement of international harmonization of criteria and terminology for stating formally the results of environmental radioactive determinations.